A differential scanning calorimetric study of chymotrypsin in the presence of added polymers

Scanning calorimetry measurements of different amounts of chymotrypsin in water alone gave a temperature of denaturation (T(d)) value of 54 degrees C. However, when high-molecular-weight poly(ethylene glycol) was added to aqueous solutions of chymotrypsin, the thermostability of the enzyme was enhanced. For example, the addition of 20% (w/w) of poly(ethylene glycol) of molecular weight of 100,000 increased the T(d/) value to 66 degrees C. In toluene containing various amounts of added water, ethyl cellulose was used to improve the thermostability of chymotrypsin. For this system, a T(d) value of 82 degrees C was obtained with a 20% (w/w/) concentration of ethyl cellulose and 2% (v/v) of added water. Polymers in these solvents interact with water, which could otherwise denature the enzyme; polymers also from complexes with enzyme molecules to produce a more stable structure. (c) 1994 John Wiley & Sons, Inc.